Cutting and Welding Unibody

tom_sprecher

tom_sprecher

Super Moderator
I tried a search but kept getting errors so I'll ask. I'm installing a roll cage in my 7 and it is so tight against the inside of the B-pillars as well as some other areas that I would like to relieve or cut away some of the interior steel to gain access for welding. I'm talking a circle about 1.75" in diameter with a hole saw. Is that legal?

Also, using a lathe has anyone ever turned down a gas shield on a MIG torch to gain access? The one on my Lincoln 175+ is pretty beefy and while I know it will get hot pretty quick I only need it for the small areas at the top of the B-pillar where the main hoop, door hoop and rear braces meet.

Another also, does anyone know of a "welding blanket", like out of leather, you can drape over stuff to keep spatter and drips from burning up and making a mess of all your hard work. A 4x4' sheet would work great.

TIA
 
I saw that after my post as well as ones made out of fiberglass. The fiberglass is a little more pricy and I wonder if they're worth it?

Plus, with a quart of resin, some Bondo and a can of spray paint in a pinch it could be used for some "at the track" body repair. ;)
 
Do whatever you need to to install your cage. A popular way to get a full weld on the bars attached at the top of the Mian hoop is to take a holelsaw to the floor, drop the main hoop down to access welding the top corners, re-raise when done, slip plates under the feet and weld the feet pads.

Beats taking off the roof!

I have one of those heavy welding blankets--mine cost about $35.00.

Fires are not fun.

Never "turn down" the MIG nozzle. If you have to, borrow a TIG welder, or use a gussett solution.

Good Luck.
 
we have always cut a hole in the roof and then patched it after welding. perfectly legal. the hole in the floor method is great but I put the cage on the rockers in the front and on the box structure behind the seat so that does not work for me.
 
When I did my 7s cage, i did as Dick described. I first took out the windsheild, and made the main hoop and halo, and moved it forward to do the main work. Then when all the parts were finalized, I moved it back, and put in the crossbar to push it into the B pillars. I used a larger hole saw for the outside skin of the roof, then a slightly smaller one for the inside roof skin to make the rewelding easier. With the holes in the roof at the right spots, acess to the impossible areas is cake.
 
When you get done with the holes for welding get a tube of Fusor or similar liquid weld for body panels. Cut the patches and glue them in. Permanent and no distortion to the roof from welding.
 
When you get done with the holes for welding get a tube of Fusor or similar liquid weld for body panels. Cut the patches and glue them in. Permanent and no distortion to the roof from welding.
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If you're a good enough welder, the roof won't distort from the heat. :P

J/K, excellent idea.
 
Is this a new cage bent just for the car or a recycled cage being swapped over?
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This is a recycled cage and it is on the rockers and rear crossmember as Dick mentioned.

For those with blankets are they Fiberglass or Canvas?

After joeg saying not to turn down the gas shield (and when I said turn down I meant in diameter not length) I experimented with how much wire from the tip distance (stand-off?) I could manage and still get a good weld. With the voltage and gas flow turned up, and simulating the angle (which is pretty much flat) and distance, I could get a pretty decent weld at almost 1.5 inches which is way more than enough. Not enough gas would make for a spongy looking weld or an "Alien" weld if the surface was not cleaned enough but I was outside and there was a breeze. 25 cfh was about right. I still wish I could see better what was being welded. I can see the puddle fine. It's where I'm going that is in the dark.

My preference would be to not cut the top as the confidence level in my and the machine's abilities to do thin stuff is not so good. I'm also lazy and hate body work. In retrospect, the amount of body work done racing this class makes me wish I was racing in a class of purpose built cars with fiberglass body panels.

Pop goes the rivet, twist goes the Dzus.
 
1.5" of stick out is a lot. Run it hot and play with the wire speed. Always start with the hardest to reach spot as your bead will build up and not give you access behind it later. Another trick is to preheat the weld area so that the bead washes in better. You wont have to run the welder quite as "hot" that way which will help you keep the bead consistant once you get down to where you can really access it.

Also, keep the cage loose at the pads... that way you can move it around a little for the best access. You might be better off cutting the drivers side harness bar out so you can pull the DS leg in to drop it down.

There's definitely a process to it and if you think ahead, you shouldn't have to cut any holes anywhere. I've yet to touch a roof and only just recently started using the drop it through the floor method when I have no other choice.
 
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